Field of the Invention
The present invention relates to a new process for preparing 3-chloro-2-vinylphenylsulfonate derivatives.
3-Chloro-2-vinylphenylsulfonates of the general formula (I) are important intermediates for the synthesis of agrochemicals. Especially the 3-chloro-2-vinylphenyl-methanesulfonate is a valuable precursors of active fungicidal ingredients (e.g. WO 2011/076699 or WO 2014/206896).
Description of Related Art
A typical synthesis of 3-chloro-2-vinylphenylsulfonates of the general formula (I) is the reaction of 3-chloro-2-vinylphenol with an aryl- or alkylsulfochloride. The synthesis of the starting material 3-chloro-2-vinylphenol is already known (EP 0511036 B1): Starting from tetrachlorocyclohexanone, what has to be prepared by chlorination of cyclohexanone, upon addition of vinylmagnesium bromide the desired vinyltetetrachlorocyclohexanol was formed and further transformed into the vinyl-2-oxa-7-bicycloheptane. Its opening upon reflux in N,N-dimethylformamide (DMF) gave finally 3-chloro-2-vinylphenol in a low total yield. Thus, this process is not suitable for commercial application. Especially the atom economy of this process is insufficient, since from 4 chlorine atoms presented in the starting tetrachlorocyclohexanone only one remains in the molecule.
Simple unprotected vinylphenols are highly prone to polymerization and further side reactions (Chemistry Letters 1980, 7, 793). Typical procedures for synthesis of these compounds include dehydration of hydroxyethyl-substituted phenyls, promoted by Al2O3, KHSO4 or H2SO4 (Journal of the American Chemical Society, 1958, 80, 3645), giving the product usually in low yield and with significant amounts of side products. A single example of a para-vinyl-phenol derivative was obtained in an ionic liquid under Microwave conditions in 56% yield (Eur. J. Org. Chem. 2008, 33, 5577), which is not feasible for industrial scale. In addition, synthesis of unprotected ortho-vinyl-phenols by elimination has not been described at all in literature. Therefore, we were surprised to find that the elimination of unprotected meta-chloro-ortho-(1-hydroxyethyl)phenol proceeds to the corresponding ortho-vinylphenol derivative in good yield.